Figure 2. Relative abundance of transgene expression across the retinal nuclear layers and co-localization with Egr-1. Representative fluorescence microscopic images of transverse sections of adult rat retina showing detection of total cells (DAPI staining), and immunoreactivities for d2EGFP (green fluorescent protein, GFP), Egr-1 and melanopsin. Animals were killed at 24:00 h. A, B: Extensive view of transgenic rat retina illustrating the abundant and uniform expression of GFP across the outer nuclear layer (ONL), photoreceptor inner segment (IS), and photoreceptor outer segment (OS) relative to the lower abundance and isolated cellular expression within the inner nuclear layer (INL) and ganglion cell layer (GCL). Vertical arrowheads indicate GFP-positive ganglion cells; horizontal arrowhead denotes a GFP-positive INL cell; horizontal arrow marks a GFP-positive process running up from the GCL. An inner zone of the ONL is indicated by a bracket (}); note the relative abundance of GFP within this inner ONL zone. C: Co-expression of GFP and Egr-1 within three cells of the INL. Note that the low level of GFP is not detectable in the merged image. D: Co-localization of GFP and Egr-1 within a single cell of the GCL. E: Absence of GFP within a giant melanopsin-positive cell of the GCL. The scale bar represents 50 μm in A,B and 20 μm in C-E.